1. Field of the Invention
The present invention relates to a generator using a permanent magnet for the field, particularly to a generator of the wind power generation system and the control method thereof. More particularly, it relates to a generator and control method thereof where the generator rotor comprises a first and second field magnets, and the magnetic pole centers of the first and second field magnets are changed in conformity to the direction of torque, and effective amount of magnetic flux is variable in conformity to speed.
2. Description of the Prior Art
In the permanent magnet field type generator according to the prior art, inductive electromotive force E is determined by a certain magnetic flux "PHgr" produced by the permanent magnet mounted on the rotor and the rotating angular speed xcfx89 of the generator. In other words, the inductive electromotive force of the generator rises in proportion to the increase in the rotating angular speed xcfx89 (speed) of the generator.
Thus, a high torque can be obtained in the low speed range, but operation in the high speed range is difficult due to limited variable range of the speed. To solve this problem, it is possible to consider expansion of the high speed operation range by field weakening control art.
Furthermore, to ensure a specified output in a wide speed range, the generator of wind power generation system is provided with a gear mechanism and pitch motor in order to meet a great variety of wind velocity conditions. In some prior arts, various phase windings of the generator are switched between low-speed winding and high-speed winding according to the main shaft speed, using a winding switching apparatus.
Expansion of the high-speed operation range by the field weakening control art referred in the description of the prior art is restricted by heat generation by weakening field current or reduction of efficiency.
When a winding switching apparatus is used to switch the winding of each phase according to the main shaft speed, the following problems arise: The number of lead wires from the generator is too many, and winding switching controller and its structure are complicated.
Complicated structure results in an increase in the weight of the nacelle of the wind power generation system, and requires the tower structure to be reinforced.
A wind power generation system comprising;
a main shaft where a vane is mounted,
a generator connected to the main shaft for transmitting the rotating power of the vane,
an inverter for converting the electric power of the generator,
a controller for controlling the inverter,
a means for controlling the pitch of the vane meeting the wind velocity requirements,
a brake, and
an anemometer/anemoscope;
the wind power generation system using the generator further characterized in that,
the generator further comprises a stator having a primary winding and a rotor having a field magnet;
the field magnet further comprises, a first field magnet having magnetic poles with different polarities arranged sequentially in the direction of rotation; and
a secondary field magnet having magnetic poles with different polarities arranged sequentially in the direction of rotation;
this second field magnet being capable of relative rotation with respect to the first field magnet;
the first and second field magnets are placed opposite to the stator magnetic pole;
a mechanism for changing the composite phase of the magnetic poles of the first and second field magnets with respect to magnetic pole of the first field magnet in conformity to the direction of the rotor torque; and
the mechanism of changing in conformity to the direction of the rotor torque has;
a means for aligning the same magnetic pole centers of the first and second field magnets in conformity to the direction of torque occurring to the rotor and the balance of magnetic action between the first and second field magnets, and
a means for displacing the magnetic pole centers of the first and second field magnets as the direction of torque occurring to the rotor is reversed.